roll ffmpeg forward for linux build against updated system ffmpeg

BUG=43778
TEST=build/install latest ffmpeg from svn then build with export

Review URL: http://codereview.chromium.org/2729003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@49227 0039d316-1c4b-4281-b951-d872f2087c98